Questions tagged [integer]
For challenges involving the manipulation of integers.
19
votes
24answers
2k views
Digital Sumorial
Given an input n, write a program or function that outputs/returns the sum of the digital sums of n for all the bases 1 to ...
18
votes
4answers
702 views
Prime containment numbers (speed edition)
This is sequence A054261
The \$n\$th prime containment number is the lowest number which contains the first \$n\$ prime numbers as substrings. For example, the number \$235\$ is the lowest number ...
21
votes
14answers
2k views
Prime containment numbers (golf edition)
This is sequence A054261.
The \$n\$th prime containment number is the lowest number which contains the first \$n\$ prime numbers as substrings. For example, the number \$235\$ is the lowest number ...
23
votes
25answers
2k views
Sort by Largest Digit(s)
Challenge:
Given a list of integer, sort descending by their single largest digit(s). The order for numbers with the same largest digit are then sorted by second largest digit, etc.
We ignore ...
17
votes
10answers
2k views
Reciprocal copycats
Let \$A\$ be a positive integer consisting of \$n\$ decimal digits \$d_1,d_2,...,d_n\$. Let \$B\$ be another positive integer.
For the purpose of this challenge, we call \$A\$ a copycat of \$B\$ if ...
20
votes
15answers
2k views
All the single eights
Given a non-empty rectangular array of integers from 0 to 9, output the amount of cells that are ...
10
votes
9answers
1k views
Through Space and Time
Introduction:
In general we usually speak of four dimensions: three space dimensions for x, y, and ...
11
votes
35answers
2k views
Print the Lost numbers
As a big fan of the Lost TV series, I always got intrigued by the sequence of numbers that repetitively appears on the episodes. These numbers are:
\$ 4, 8, 15, 16, 23, 42\$ (A104101)
Using any ...
14
votes
26answers
2k views
The inverse Collatz Conjecture
I think the Collatz Conjecture is already well-known. But what if we invert the rules?
Start with an integer n >= 1.
Repeat the following steps:
If n is even, multiply it by 3 and add 1.
If n is ...
20
votes
22answers
1k views
New Neighbour Sequence
The non-negative integers are bored of always having the same two* neighbours, so they decide to mix things up a little. However, they are also lazy and want to stay as close as possible to their ...
17
votes
19answers
2k views
The Written Digits Sequence
Here's a reasonably trivial sequence which is not in the Online Encyclopedia of Integer Sequences.
Start with an empty sequence then define each term as the number of characters required to write out,...
9
votes
24answers
932 views
Multiplicative undelta
Let us define the "multiplicative deltas" of values \$[\; a_0, \cdots a_N, \;]\$ as:
$$
[\; a_1 / a_0, \cdots, a_{i+1} / a_i, \cdots, a_N / a_{N-1} \;]
$$
The reverse operation - namely "...
13
votes
16answers
814 views
Length of a UTF-8 byte sequence
Determine the length of a UTF-8 byte sequence given its first byte. The following table shows which ranges map to each possible length:
...
15
votes
9answers
601 views
Stagger, stack, sum
Inspired by this Stack Overflow question.
The challenge
Input
An array of square matrices containing non-negative integers.
Output
A square matrix built from the input matrices as follows.
Let \$...
26
votes
18answers
3k views
Make them sum to 10,000
We've recently reached the threshold of 10,000 questions on PPCG. Hooray! Let's celebrate this with a simple challenge.
Input
Two integers \$A\$ and \$B\$, both in \$[1..9999]\$, such that \$A+B<...
-1
votes
1answer
111 views
Every positive integer can be written as the sum of 3 palindrome integers. Wha'ts the largest possible palindrome integer for each integer n? [duplicate]
Let n be a positive integer then n = a + b + c for some a, b, and c that are palindrome integers. What is the largest possible integer ...
17
votes
18answers
4k views
Longest Repeating Subsequence of a Single Digit
Challenge:
Given a positive integer, output the longest single-digit subsequence that occurs at least twice, AND has boundaries of another digit (or the start/end of the integer).
An example:
Input:...
10
votes
7answers
629 views
Whose neighbours are hostile?
Introduction
For the purposes of this challenge, we will define the neighbours of an element \$E\$ in a square matrix \$A\$ (such that \$E=A_{i,j}\$) as all the entries of \$A\$ that are immediately ...
31
votes
41answers
5k views
Half, Half Half, and, Half
Consider the following number sequence:
\$ 0, \frac{1}{2}, \frac{1}{4}, \frac{3}{4}, \frac{1}{8}, \frac{3}{8}, \frac{5}{8}, \frac{7}{8}, \frac{1}{16}, \frac{3}{16}, \frac{5}{16}, \frac{7}{16}, \...
16
votes
18answers
4k views
Simplistic Lava Lamp
Introduction:
I think everyone knows what a Lava Lamp is, but in case they do not:
(Image source)
They're basically glass tubes that contain wax in a translucent liquid. The bottom part is heated ...
21
votes
15answers
2k views
Crown hundred crownty crown
I noticed a certain game had a peculiar life counter, which instead of stopping at 999, gained a new digit – the next number was crown hundred or ...
14
votes
15answers
1k views
Missing numbers in arithmetic sum
Challenge
Giving a valid arithmetic sum with some missing numbers, output the full expression.
Example:
...
6
votes
20answers
411 views
Find the \$\left(n^2\right)^\text{th }n\$-gonal number
Given a non-negative integer, \$n\$, yield the \$(n^2)^\text{th } n\$-gonal number.
Further Detail:
The \$x\$-gonal numbers, or polygonal numbers, are also known as the two-dimensional figurate ...
12
votes
11answers
1k views
Codegolf Rainbow : Fun with Integer-Arrays
Introduction:
(Source: Wikipedia)
When we look at a rainbow it will always have the colors from top to bottom:
Red; orange; yellow; green; blue; indigo; violet
If we look at these individual rings, ...
15
votes
21answers
1k views
Fill up to duplicate ranges
Let \$L\$ be a list of positive integers with no particular ordering, and which can contain duplicates. Write a program or function which outputs a list of positive integers \$M\$ (whose ordering is ...
25
votes
15answers
2k views
Toggle some bits and get a square
Given an integer \$N>3\$, you have to find the minimum number of bits that need to be inverted in \$N\$ to turn it into a square number. You are only allowed to invert bits below the most ...
17
votes
34answers
950 views
Calculate power series result [duplicate]
Related: Calculate Power Series Coefficients
Given a positive integer \$X\$ and a max exponent (Also a positive integer too) \$N\$ calculate the result of a power series. Example:
$$X^0+X^1+X^2+\...
18
votes
8answers
712 views
Spiral neighbourhoods
If we take the natural numbers and roll them up counter clock-wise into a spiral we end up with the following infinite spiral:
...
13
votes
12answers
2k views
Small Ramsey Numbers
Background: the Ramsey number \$R(r,s)\$ gives the minimum number of vertices \$v\$ in the complete graph \$K_v\$ such that a red/blue edge coloring of \$K_v\$ has at least one red \$K_r\$ or one blue ...
17
votes
7answers
619 views
Stacked digit staircases
Given positive integers \$w\$ and \$h\$ output \$w\$ columns and \$h\$ rows of text as described below.
The first row begins with 11 0s, the second row with 10 <...
-1
votes
7answers
396 views
Calculate the sum of all odd digits of pi in range [duplicate]
Introduction
In the not so distant future with the AI revolution, we will need a way to solve their captchas to prove we're not humans.
This challenge was inspired by CommitStrip.
Challenge
One ...
7
votes
10answers
530 views
How many bytes is it
This time, we want render the count of bytes in a human readable way to user. Let's write a program (a full one or a function or other acceptable formats) to do this.
Input
An non-negative integer, ...
25
votes
30answers
2k views
Let's design a digit mosaic
Challenge
Given a positive integer \$N\$, repeat each of its digits \$d_1, d_2, d_3, \cdots, d_n\$ a number of times corresponding to its position in \$N\$. In other words, each digit \$d_k\$ should ...
24
votes
29answers
2k views
Replace me by the sum of my cyclic successors!
I have a simple challenge for you this time. Given an array of positive integers A (or the equivalent in your language), replace each entry Ai with the sum of the next Ai elements of A, cycling back ...
16
votes
8answers
570 views
Classify a region by its slope
Definitions
The kth ring of a square matrix of size N, where 1 ≤ k ≤ ceiling(N/2) is the list formed by the elements of the kth and (N-k+1)th rows and columns, but without the first and last k-1 ...
21
votes
39answers
3k views
33
votes
42answers
3k views
Up and down, up and down
Challenge:
Given a positive integer input n, create a vector that follows this pattern:
0 1 0 -1 -2 -1 0 1 2 3 2 1 0 -1 -2 -3 -4 -3 -2 -1 ... ±(n-1) ±n
...
3
votes
0answers
161 views
Make Three from One [duplicate]
Given a single digit integer and a three digit integer, output a mathematical formula that uses only the single digit and a given list of operators to equal the three digit integer.
Input: A one ...
24
votes
15answers
1k views
Modular broadcasting
This challenge is related to some of the MATL language's features, as part of the May 2018 Language of the Month event.
Introduction
In MATL, many two-input functions work element-wise with ...
24
votes
10answers
2k views
Knight Distance
In Chess, a Knight on grid (x, y) may move to (x-2, y-1), (x-2, y+1), (x-1, y-2), (x-1, y+2), (x+1, y-2), (x+1, y+2), (x+2, y-1), (x+2, y+1) in one step. Imagine an infinite chessboard with only a ...
3
votes
2answers
68 views
Generate lowest degree polynomial from sequence [duplicate]
Introduction
A sequence of numbers is passed in as the input. The program has to generate the lowest degree polynomial possible. This was my first programming project in college and it would be ...
13
votes
13answers
1k views
12
votes
8answers
755 views
Digit Occurrences
Input:
A list of integers (which will never contain a zero)
Output:
A list of the same size with counts based on the following:
If the current item is negative: Look at all items before this item, ...
21
votes
16answers
1k views
Interval Notations
Challenge:
Input:
Two integer parameters a and b (where a<b and the difference is at ...
23
votes
15answers
2k views
Not Quite Roman Ternary
Given an integer n ≥ 0 , output it in a non-positional base-3 notation, using digits 139ABCDE… and a 1-character separator. Every digit is a consecutive power of 3 ...
32
votes
33answers
2k views
Digits in their lanes
Input:
A list of integers
Output:
Put each digit (and the minus sign) in its own lane, in the order -0123456789, ignoring any duplicated digits.
Example:
Input:...
30
votes
47answers
4k views
Which Card is it?
Introduction
Long ago, when I used to code card games with usual playing cards, I used to specify a number for each card and call a function with some number to get a card. This somewhat inspired me ...
20
votes
14answers
1k views
Is this a truncated triangular number?
Related OEIS sequence: A008867
Truncated triangular number
A common property of triangular numbers is that they can be arranged in a triangle. For instance, take 21 and arrange into a triangle of <...
11
votes
3answers
824 views
Crazy but Rational Bases
We have many challenges based on base 10, base 2, base 36, or even base -10, but what about all the other rational bases?
Task
Given an integer in base 10 and a rational base, return the integer in ...
12
votes
5answers
174 views
Reduced Factorization Leader Changes
tl;dr: Output the values where the reduced prime factorization leader changes.
Every positive integer has a unique prime factorization. Let's call the reduced prime factorization just the list of ...
